Device for detecting acoustic waves

ABSTRACT

A device for detecting acoustic waves may include a housing having a housing wall with an inner surface, and an acoustic wave sensor provided at least partially inside the housing and configured to detect acoustic waves. The inner surface of the housing wall is made in at least half of its entire area of a thermally insulating material.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/587,535, filed May 5, 2017, which claims priority to German PatentApplication Serial No. 10 2016 108 421.2, which was filed May 6, 2016,all of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

Various embodiments relate generally to a device for detecting acousticwaves including a housing and an acoustic wave sensor.

BACKGROUND

A key performance parameter of sensors in general is the signal-to-noiseratio which is directly linked to both the sensitivity and theresolution of the sensors. This also applies to devices for detectingacoustic waves. Low noise levels are a mandatory prerequisite forachieving high signal-to-noise ratios.

A specific noise source of devices for detecting acoustic waves arisesfrom thermal fluctuations of gas present inside the housing that inducepressure fluctuations, i.e. acoustic waves, that may contribute to thenoise level of the device.

SUMMARY

According to various embodiments, a device for detecting acoustic wavesis provided. The device may include a housing having a housing wall withan inner surface, and an acoustic wave sensor provided at leastpartially inside the housing and configured to detect acoustic waves.The inner surface of the housing wall is made in at least half of itsentire area of a thermally insulating material.

According to various embodiments, a device for detecting acoustic wavesis provided. The device may include a housing having a metal housingportion, a layer formed on an inner surface of the metal housingportion, and an acoustic wave sensor provided at least partially insidethe housing and configured to detect acoustic waves. The layer is madeof a material having a thermal conductivity that is smaller than thethermal conductivity of the metal housing portion.

According to various embodiments, a device for detecting acoustic wavesis provided. The device may include a housing having a housing wall, andan acoustic wave sensor provided at least partially inside the housingand configured to detect acoustic waves. The housing wall comprises aportion extending from the inner surface to the outer surface of thehousing wall, the portion being entirely made of a thermally insulatingmaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. The drawings are not necessarilyto scale, emphasis instead generally being placed upon illustrating theprinciples of the invention. In the following description, variousembodiments of the invention are described with reference to thefollowing drawings, in which:

FIG. 1 shows a schematic view of a device for detecting acoustic waves;

FIG. 2 shows a schematic view of a modified device for detectingacoustic waves; and

FIG. 3 shows a schematic view of another modified device for detectingacoustic waves.

DESCRIPTION

The following detailed description refers to the accompanying drawingsthat show, by way of illustration, specific details and embodiments inwhich the invention may be practiced.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration”. Any embodiment or design described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments or designs.

FIG. 1 shows a device 100 for detecting acoustic waves. The device mayinclude a housing 102 having a housing wall 104 with an inner surface106 and an outer surface 108. The device 100 may include an acousticwave sensor 110 provided at least partially inside the housing 102 andconfigured to detect acoustic waves. As indicated in FIG. 1, the sensor110 may include a membrane 111 that may be caused to vibrate by theacoustic waves to be detected, thereby generating a detection signalindicative of the acoustic wave energy and/or intensity. The innersurface 106 of the housing wall 104 may be made in at least half of itsentire area of a thermally insulating material.

Thermally induced noise in devices for detecting acoustic waves may begenerated by a time-varying energy input into the inside of the housing102 leading to a temperature rise of gas present inside the housing 102and thereby to an increase in gas pressure. The time-varying energyinput may either originate from the exterior of the housing or from anisothermal heat exchange with a lining at the inner surface of thehousing wall made of a material with a high thermal conductivity such asmetal. The temperature of the gas may be thereby increased above thetemperature of a heat sink to which the housing 102 is coupled via athermal link. Such a heat sink may be a holder of the device 100 or thesurrounding atmosphere. Via the thermal link a heat exchangesubsequently occurs with the heat sink after the energy input into theinside of the housing 102, thereby reducing the temperature of the gasinside the housing 102 and, hence, its pressure. This in turn leads topressure fluctuations of the gas inside the housing 102, i.e. toacoustic waves that may be detected as noise by the acoustic wave sensor110.

By making the inner surface 106 of the housing wall 104 in at least halfof its entire area of a thermally insulating material, the thermal linkbetween the interior of the housing 102 and the exterior of the housing102 that may act as a heat sink is reduced as compared to housingsentirely made of metal which is generally the case in common devices fordetecting acoustic waves. In this way, the frequencies of pressurefluctuations of the gas inside the housing 102 induced by a time-varyingenergy input into the interior of the housing 102 can be reducedcompared to common metal housings, thereby shifting the frequency of thethermally induced noise to lower frequencies, e.g. outside of thefrequency range of a signal to be detected by the acoustic wave sensor110. Consequently, the signal-to-noise ratio of the device 100 can beimproved, since the noise power in the frequency range of the signal isreduced.

The acoustic wave sensor 110 may be configured as a microphone, e.g. amicrophone employed in a telephone such as a MEMS microphone. In thiscase, the frequency range of the signal to be detected by the acousticwave sensor 110 is the audible frequency range (about 20 Hz to about 20kHz). Here, the frequencies of the thermally induced noise may beshifted down to below 20 Hz, i.e. outside of the audible frequencyrange, thereby reducing the noise in the frequency range of the signaland increasing the signal-to-noise ratio of the microphone.

The frequency range of the signal is the frequency range between thelowest and the highest frequency components of the signal. The frequencycomponents of the signal may be determined by Fourier transformation orany other suitable spectral transformation.

The suppression of thermally induced noise in the device 100 fordetecting acoustic waves may be the more efficient the lower the thermalconductivity of the thermally insulating material is. The thermalconductivity of the thermally insulating material may be less than about20 W/(m·K) or even less than about 10 W/(m·K). In an exemplary device,the thermal conductivity of the thermally insulating material may beeven less than about 5 W/(m·K). The thermal conductivity of thethermally insulating material can be as low as about 0.02 W/(m·K) whichnearly corresponds to the thermal conductivity of air. Such a lowthermal conductivity may be achieved, e.g., with expanded polystyrenethat relies on thermal insulation by air. An even lower thermalconductivity may be provided by a vacuum shield that may bemicrofabricated.

In an exemplary device 100, the housing wall 104 may have a portion 130(see FIG. 1) extending between the inner surface 106 and the outersurface 108 of the housing wall 104, the portion 130 being entirely madeof the thermally insulating material. This means that this portion 130extends over the full thickness of the housing wall 104. Anotherparameter that may directly influence the suppression of thermallyinduced noise may be the area of the inner surface 106 that is made ofthe thermally insulating material. The suppression of thermally inducednoise may be the more efficient the higher the area of the inner surface106 of the housing wall 104 made of the thermally insulating materialis. The inner surface 106 of the housing wall 104 may be made in atleast 70% or even in at least 90% of its entire area of the thermallyinsulating material. In an exemplary device 100 for detecting acousticwaves, the entire inner surface 106 of the housing wall 104 may be madeof the thermally insulating material.

As shown in FIG. 1, the housing wall 104 may include a layered portion112. The layered portion 112 may include a plurality of layers 112 a,112 b stacked in a thickness direction of the housing wall 104. Thelayered portion 112 may include an inner layer 112 a forming at least apart of the inner surface 106 of the housing wall 104, and at least oneouter layer 112 b positioned closer to the outer surface 108 of thehousing wall 104 than the inner layer 112 a.

Although the device 100 shown in FIG. 1 includes a layered portion 112with only two layers 112 a, 112 b, layered portions 112 with more thantwo layers are also conceivable.

The inner layer 112 a may be made at least in part of the thermallyinsulating material.

In various embodiments, one outer layer 112 b may be made at least inpart of a material having a higher thermal conductivity than thematerial of the inner layer 112 a. The outer layer 112 b may be made ofan electrically conductive material such as a metal to support EMI(electromagnetic interference) protection. The outer layer 112 b made ofa material with a higher thermal conductivity may form at least a partof the outer surface 108 of the housing wall 104.

The device 100 for detecting acoustic waves does not necessarily have tobe employed in a telephone. An exemplary device 100 for detectingacoustic waves may be employed in a gas analyzer configured to analyzegases based on the photo-acoustic effect. In such a gas analyzer, a gasto be analyzed is excited by an excitation radiation such as light, e.g.emitted by a laser e.g. in the visible or in the ultraviolet (UV)frequency range in a time-varying fashion. Infrared (IR) excitationradiation is also conceivable. The energy of the excitation radiationmay be chosen depending on particles that are to be detected in the gasto be analyzed. In various embodiments, the frequency may be chosen tomatch an atomic or molecular transition characteristic to certainparticles to be detected in the analyzed gas. In this way, theseparticles can be selectively excited by the excitation radiation.

During the subsequent relaxation of the excited atomic or molecularenergy states, thermal energy is generated. Since the gas to be analyzedis excited in a time-varying fashion, e.g. periodically, thermal energyis also generated in a time-varying fashion leading to pressurefluctuations in the gas, i.e. acoustic waves that may be detected by theacoustic wave sensor 110.

The gas to be analyzed may be received inside the housing 102 of thedevice 100 shown in FIG. 1. The excitation radiation may be supplied tothe gas to be analyzed inside the housing 102 through one or moreoptically transparent window portions 114 provided in the housing wall104.

By selecting the energy of the excitation radiation to match acharacteristic atomic or molecular transition energy of particles to bedetected in the analyzed gas, the amount of acoustic energy generatedduring the relaxation of the excited states and detected by the acousticwave sensor 110 is indicative of a certain content of the particles tobe detected in the analyzed gas.

To avoid a temperature rise of the housing wall 104, e.g. by theexcitation radiation, the inner layer 112 a may be made at least in partor even entirely of a material which is optically transparent.Depending, e.g. on the frequency of the excitation radiation in case ofa gas analyzer, the optically transparent material may be opticallytransparent in the infrared and/or in the visible and/or in theultraviolet frequency range.

In an exemplary device, the optically transparent material may have atransmittance of at least about 80% or even of at least about 90% in theinfrared and/or in the visible and/or in the ultraviolet frequencyrange.

In order to inhibit or reduce the input of electromagnetic radiationinto the housing 102 from the exterior of the housing 102, at least oneouter housing wall layer 112 b may be made at least in part or entirelyof a material which is optically opaque. In case of a gas analyzer, anopaque outer housing wall layer 112 b may also avoid losses ofexcitation radiation through the housing wall 104.

The optically opaque material may be optically opaque in the infraredand/or in the visible and/or in the ultraviolet frequency range.

The optically opaque material may have a reflectance of at least about80% or even of at least about 90% in the infrared and/or the visibleand/or in the ultraviolet frequency range. This may be achieved with anouter layer 112 b made at least in part or entirely of a metal.

An exemplary device 100 configured as a gas analyzer may have an innerlayer 112 a made of an optically transparent material with a low thermalconductivity as defined above, and an outer layer 112 b acting as areflector to provide an efficient gas excitation.

As shown in FIG. 1, the housing 102 may include a substrate 116 on whichthe acoustic wave sensor 110 is mounted, and a lid 118. Thus the housingwall 104 may also be comprised of the substrate 116 and the lid 118. Thesubstrate 116 may be made of a semiconductor such as silicon. The lid118 may include a part of the layered portion 112 of the housing wall102 or may be even identical to the layered portion 112 of the housingwall 102.

The substrate 116 may include an acoustic port 120 in close proximity tothe mounting position of the acoustic wave sensor 110 to efficientlydirect acoustic waves to the acoustic wave sensor 110.

In order to provide an efficient suppression of thermally induced noise,at least a part of the substrate 116 facing to the inside of the housing102 may be coated with a thermally insulating substrate material. Inother words, a part of the substrate 116 or the entire surface of thesubstrate 116 facing to the inside of the housing 102 may be coated witha thermally insulating substrate material.

The thermal conductivity of the thermally insulating substrate materialmay be less than about 20 W/(m·K) or even less than about 10 W/(m·K). Inan exemplary device, the thermal conductivity of the thermallyinsulating substrate material may be even less than about 5 W/(m·K).

Besides the acoustic wave sensor 110, the substrate 116 may also includean electronic circuit 122 mounted thereon inside the housing 102, e.g.for processing signals such as electric signals generated by the sensor110, e.g. by its vibrating membrane 111. In order to provide anefficient suppression of thermally generated noise, the electroniccircuit 122 may be at least in part coated with thermally insulatingsubstrate material 124.

The electronic circuit 122 may include a printed circuit board and/or anelectronic component such as an application specific integrated circuit(ASIC). The thermally insulating substrate material may be coated on asurface of the printed circuit board and/or of the electronic component.Thermally insulating material may be also provided on the membrane 111of the sensor 110 and/or on bonding wires.

In an exemplary device 100, no open metallization is present inside thehousing 102, e.g. no open metallization of the electronic circuit 122.This may be achieved by avoiding any bonding wires inside the housing102, e.g. by providing electrical contacts by flip-chip bonding insidethe housing 102.

The thermally insulating material of the housing wall 104 and/or thethermally insulating material on the substrate 116 may be selected fromglass materials, plastic materials such as polymers, Teflon or a moldcompound, and oxides such as metal oxides.

It should be noted that the inner surface 106 of the housing wall 104may be made in different portions of different thermally insulatingmaterials. Also the substrate 116 or the components mounted thereon maybe coated in different portions thereof with different thermallyinsulating materials.

The configuration shown in FIG. 1 with the sensor 110 mounted on thesubstrate 116 and the acoustic port 120 provided in the substrate 116 isreferred to as “bottom-port” configuration.

A device 200 for detecting acoustic waves according to a mirroredconfiguration with an acoustic wave sensor 210 mounted on a lid 218 andan acoustic port 220 provided in the lid 218 is shown in FIG. 2. Thisconfiguration is referred to as “top-port” configuration. In FIG. 2 thesame reference numerals are used for the same elements as in FIG. 1,however, enhanced by the number 100.

In the exemplary device shown in FIG. 2 also an electronic component 222is mounted on the lid 218. In this way, the length of wires between anacoustic wave sensor 210 and the electronic component 222 can be keptshort, thereby reducing their contribution to the overall thermalconductivity of the thermal link between the interior and the exteriorof the housing 102.

The above concepts described with respect to device 100 according to the“bottom-port” configuration apply also to the device 200 shown in FIG. 2according to the “top-port” configuration.

A modified device 300 for detecting acoustic waves according to the“top-port” configuration is shown in FIG. 3. In FIG. 3 the samereference numerals are used for the same elements as in FIG. 1, however,enhanced by the number 200.

The exemplary device 300 shown in FIG. 3 differs from the device shownin FIG. 1 in that the acoustic port 320 is provided in the lid 318.Similar to the device 100 of FIG. 1, the electronic component 322 andthe acoustic wave sensor 310 are mounted on the substrate 316.

In the configuration shown in FIG. 3, walls 326 of the acoustic wavesensor 310 define with the substrate 316 an enclosed volume 328 thatmight be the origin of the above-discussed noise.

In order to suppress this kind of noise, the walls 326 of the acousticwave sensor 310 may include thermally insulating material 330 at a sidethereof delimiting the enclosed volume 328. The thermally insulatingmaterial may include the above-described thermally insulating materials,e.g. oxides and polymers.

The other concepts described with respect to the device 100 shown inFIG. 1 apply also to the device 300 shown in FIG. 3.

In the following, various aspects of this disclosure will beillustrated:

Example 1 is a device for detecting acoustic waves. The device mayinclude a housing having a housing wall with an inner surface, and anacoustic wave sensor provided at least partially inside the housing andconfigured to detect acoustic waves. The inner surface of the housingwall is made in at least half of its entire area of a thermallyinsulating material.

In Example 2, the subject matter of Example 1 can optionally includethat the thermal conductivity of the thermally insulating material isless than 20 W/(m·K).

In Example 3, the subject matter of Example 2 can optionally includethat the thermal conductivity of the thermally insulating material isless than 10 W/(m·K).

In Example 4, the subject matter of Example 3 can optionally includethat the thermal conductivity of the thermally insulating material isless than 5 W/(m·K).

In Example 5, the subject matter of any one of Examples 1 to 4 canoptionally include that the inner surface of the housing wall is made inat least 70% of its entire area of the thermally insulating material.

In Example 6, the subject matter of Example 5 can optionally includethat the inner surface of the housing wall is made in at least 90% ofits entire area of the thermally insulating material.

In Example 7, the subject matter of any one of Examples 1 to 6 canoptionally include that the housing wall includes a layered portionincluding a plurality of layers stacked in a thickness direction of thehousing wall. The layered portion may include an inner layer forming atleast a part of the inner surface of the housing wall, and at least oneouter layer positioned closer to an outer surface of the housing wallthan the inner layer.

In Example 8, the subject matter of Example 7 can optionally includethat the inner layer is made at least in part of the thermallyinsulating material.

In Example 9, the subject matter of Example 8 can optionally includethat at least one outer layer is made at least in part of a materialhaving a higher thermal conductivity than the material of the innerlayer.

In Example 10, the subject matter of Example 9 can optionally includethat one outer layer forming at least a part of the outer surface of thehousing wall has a higher thermal conductivity than the inner layer.

In Example 11, the subject matter of any one of Examples 9 or 10 canoptionally include that at least one outer layer is made at least inpart of a metal.

In Examples 12, the subject matter of any one of Examples 7 to 11 canoptionally include that the inner layer is made at least in part of amaterial which is optically transparent.

In Example 13, the subject matter of Example 12 can optionally includethat the optically transparent material is optically transparent in theinfrared and/or in the visible and/or in the ultraviolet frequencyrange.

In Example 14, the subject matter of Example 13 can optionally includethat the optically transparent material has a transmittance of at least80% in the infrared and/or in the visible and/or in the ultravioletfrequency range.

In Example 15, the subject matter of Example 14 can optionally includethat the optically transparent material has a transmittance of at least90% in the infrared and/or in the visible and/or in the ultravioletfrequency range.

In Example 16, the subject matter of any one of Examples 7 to 15 canoptionally include that at least one outer layer is made at least inpart of a material which is optically opaque.

In Example 17, the subject matter of Example 16 can optionally includethe optically opaque material is optically opaque in the infrared and/orin the visible and/or in the ultraviolet frequency range.

In Example 18, the subject matter of Example 17 can optionally includethat the optically opaque material has a reflectance of at least 80% inthe infrared and/or the visible and/or in the ultraviolet frequencyrange.

In Example 19, the subject matter of Example 18 can optionally includethat the optically opaque material has a reflectance of at least 90% inthe infrared and/or the visible and/or in the ultraviolet frequencyrange.

In Example 20, the subject matter of any one of Examples 1 to 19 canoptionally include that the housing includes a substrate on which theacoustic wave sensor is mounted, and a lid.

In Example 21, the subject matter of Example 20 and of any one ofExamples 7 to 19 can optionally include that the lid includes a layeredportion.

In Example 22, the subject matter of any one of Examples 20 or 21 canoptionally include that at least a part of the substrate facing to theinside of the housing is coated with a thermally insulating substratematerial.

In Example 23, the subject matter of Example 22 can optionally includethat the thermal conductivity of the thermally insulating substratematerial is less than 20 W/(m·K).

In Example 24, the subject matter of Example 23 can optionally includethat the thermal conductivity of the thermally insulating substratematerial is less than 10 W/(m·K).

In Example 25, the subject matter of Example 24 can optionally includethat the thermal conductivity of the thermally insulating substratematerial is less than 5 W/(m·K).

In Example 26, the subject matter of any one of Examples 20 to 25 canoptionally include that the substrate includes an electronic circuitmounted thereon inside the housing. The electronic circuit is at leastin part coated with the thermally insulating substrate material.

In Example 27, the subject matter of Example 26 can optionally includethat the thermally insulating substrate material is coated on a surfaceof at least one of a printed circuit board, of an electronic component,a membrane of the acoustic wave sensor, and of a bonding wire.

In Example 28, the subject matter of any one of Examples 1 to 27 canoptionally include that the acoustic wave sensor is configured as amicrophone.

In Example 29, the subject matter of any one of Examples 1 to 28 canoptionally include that the housing wall includes an opticallytransparent window portion providing an optical port to the inside ofthe housing.

In Example 30, the subject matter of any one of Examples 1 to 29 canoptionally include that the thermally insulating material and/or thethermally insulating substrate material is selected from glassmaterials, plastic materials, and oxides.

In Example 31 the subject matter of any one of Examples 1 to 30 canoptionally include that the housing wall comprises a portion extendingfrom the inner surface to the outer surface of the housing wall, theportion being entirely made of the thermally insulating material.

Example 32 is a device for detecting acoustic waves. The device mayinclude a housing having a metal housing portion, a layer formed on aninner surface of the metal housing portion, and an acoustic wave sensorprovided at least partially inside the housing and configured to detectacoustic waves. The layer is made of a material having a thermalconductivity that is smaller than the thermal conductivity of the metalhousing portion.

Example 33 is a device for detecting acoustic waves. The device mayinclude a housing having a housing wall with an inner surface and anouter surface, and an acoustic wave sensor provided at least partiallyinside the housing and configured to detect acoustic waves. The housingwall includes a portion extending from the inner surface to the outersurface of the housing wall, the portion being entirely made of athermally insulating material.

In Example 34, the subject matter of Example 33 can optionally includethat the thermal conductivity of the thermally insulating material isless than 20 W/(m·K).

In Example 35, the subject matter of Example 34 can optionally includethat the thermal conductivity of the thermally insulating material isless than 10 W/(m·K).

In Example 36, the subject matter of Example 35 can optionally includethat the thermal conductivity of the thermally insulating material isless than 5 W/(m·K).

While the invention has been particularly shown and described withreference to specific embodiments, it should be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims. The scope of the invention is thusindicated by the appended claims and all changes which come within themeaning and range of equivalency of the claims are therefore intended tobe embraced.

What is claimed is:
 1. A device for detecting acoustic waves,comprising: a housing including a housing wall, a substrate, and a lidopposite to the substrate, wherein the housing wall, the substrate, andthe lid define an interior of the housing; and an acoustic wave sensormounted at least partially on an inner surface of the lid, the innersurface of the lid facing the substrate; wherein the acoustic wavesensor is configured to detect acoustic waves, wherein the housing wallcomprises a layered portion comprising a plurality of layers stacked ina thickness direction of the housing wall, and wherein the layeredportion comprises an inner layer forming at least a part of an innersurface of the housing wall, and at least one outer layer positionedcloser to an outer surface of the housing wall than the inner layer, andwherein the inner layer is made at least in part of a material which isoptically transparent.
 2. The device of claim 1, wherein the innersurface of the housing wall is made in at least half of its entire areaof a thermally insulating material.
 3. The device of claim 2, whereinthe thermal conductivity of the thermally insulating material is lessthan 20 W/(m·K).
 4. The device of claim 2, wherein the inner surface ofthe housing wall is made in at least 70% of its entire area of thethermally insulating material.
 5. The device of claim 1, wherein atleast one outer layer is made at least in part of a material having ahigher thermal conductivity than the material of the inner layer;wherein one outer layer forming at least a part of the outer surface ofthe housing wall has a higher thermal conductivity than the inner layer.6. The device of claim 5, wherein at least one outer layer is made atleast in part of a metal.
 7. The device of claim 1, wherein theoptically transparent material is optically transparent in at least oneof the following frequency ranges: the infrared frequency range; thevisible frequency range; the ultraviolet frequency range.
 8. The deviceof claim 7, wherein the optically transparent material has atransmittance of at least 80% in at least one of the following frequencyranges: the infrared frequency range; the visible frequency range; theultraviolet frequency range.
 9. The device of claim 1, wherein the atleast one outer layer is made at least in part of a material which isoptically opaque.
 10. The device of claim 9, wherein the opticallyopaque material is optically opaque in at least one of the followingfrequency ranges: the infrared frequency range; the visible frequencyrange; the ultraviolet frequency range.
 11. The device of claim 10,wherein the optically opaque material has a reflectance of at least 80%in at least one of the following frequency ranges: the infraredfrequency range; the visible frequency range; the ultraviolet frequencyrange.
 12. The device of claim 1 further comprising: an acoustic portprovided in the lid.
 13. The device of claim 12, wherein the acousticsensor is mounted over the acoustic port.
 14. The device of claim 1further comprising: an electronic circuit mounted on the inner surfaceof the lid, wherein the electronic circuit is at least in part coatedwith a second thermally insulating substrate material.
 15. The device ofclaim 1, wherein the acoustic wave sensor is configured as a microphone.16. The device of claim 1, wherein the housing wall comprises anoptically transparent window portion providing an optical port to theinside of the housing.
 17. A device for detecting acoustic waves,comprising: a housing including a housing wall, a substrate, and a lidopposite to the substrate, wherein the housing wall, the substrate, andthe lid define an interior of the housing; and an acoustic wave sensorprovided at least partially inside the housing and configured to detectacoustic waves, the acoustic wave sensor mounted on a first surface ofthe substrate facing the lid; an acoustic port provided in the lid;wherein the housing wall comprises a layered portion comprising aplurality of layers stacked in a thickness direction of the housingwall; wherein the layered portion comprises an inner layer forming atleast a part of the inner surface of the housing wall, and at least oneouter layer positioned closer to an outer surface of the housing wallthan the inner layer with the inner layer is made at least in part of amaterial which is optically transparent, and wherein the lid comprises alayered portion.
 18. The device of claim 17, wherein the housing isconfigured to hold a gas in the interior of the housing.
 19. The deviceof claim 1, wherein the housing is configured to hold a gas in theinterior of the housing.